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Golden Retriever Lifetime Study

Understanding: Immunology

The National Cancer Institute estimates that a staggering 12 million cats and dogs will be diagnosed with cancer each year, and surveys show that cancer is a major health concern of dog and cat owners. Although great strides have been made in cancer treatments in pets, the disease remains a leading cause of death in our canine and feline friends, especially as they age.

Veterinary oncologists are constantly searching for new ways to improve the odds that our pets will survive a cancer diagnosis. Though progress has been painfully slow for the last two decades, hope is on the horizon in the form of immunotherapy, a new type of cancer treatment that’s revolutionizing human cancer medicine, and is making its way into the veterinary world.

Enlisting a Powerful Ally to Fight Cancer

The basic premise of immunotherapy is finding ways to direct the body’s own immune system, responsible for destroying invading organisms and abnormal cells, toward combating cancer. Cancer cells use a variety of strategies to make themselves invisible to the immune system. The goal of immunotherapy is to break down these defenses so the cancer cells are recognized by our immune system, which then goes in for the kill.

Although the concept of immunotherapy has been around for more than 100 years, it took advances in our understanding of the immune system, coupled with new technologies, to make manipulation of the immune system possible.

Immunotherapy and Its Cancer Fighting Strategies

Several different types of cancer treatments fall under the category of immunotherapy. Each type targets a different vulnerability in tumor growth and spread to slow down, stop or even shrink a particular tumor. Common types of immunotherapy include:

Biologic response modifiers – These include substances that non-specifically stimulate the immune system. Biologic response modifiers were some of the earliest forms of immunotherapy. An example is Bacillus Calmette-Guerin (BCG), an inactivated form of Mycobacterium bovis, one of the causes of tuberculosis. When injected near a tumor, BCG stimulates the immune system in a non-specific way to attack the tumor. BCG has side effects but still is occasionally used to treat some cancers in people. Other bacteria, and even viruses, have been used to treat cancers in this way, and this remains an active area of research.

Cytokines, growth factors, hormones – These include substances already involved in stimulating the immune system that are given at higher doses than what would normally be made in the body. An example is the use of interferons to stimulate anti-tumor responses. Although popular several years ago, the side effects noted from giving cancer patients high doses of these factors have made this type of therapy less useful.

Tumor vaccines – There are many different types of anti-tumor vaccines, each employing a different strategy. Vaccines are created that “aim” the immune system directly to the tumor in a specific fashion in order to spare normal tissues – similar to how vaccines against viruses tend to be very specific against one pathogen. For example, one type of tumor vaccine stimulates antibodies directed to a surface marker only present on a specific tumor. This is a very active area of research in both human and veterinary medicine.

Cell transfer – These therapies include the transfer of immune effector cells – cells capable of killing abnormal cells – that have been altered in some way to target them specifically to tumors.

Many oncologists feel that immunotherapy holds promise as both a stand-alone anti-cancer therapy and as an adjunct to conventional anti-cancer therapies such as surgery and chemotherapy. The attractiveness of immunotherapy is the way it can be specifically targeted to cancer cells while minimizing collateral damage to normal cells, a big problem that plagues conventional cancer therapies such as radiation therapy.

Morris Animal Foundation’s Investment in Immunotherapy

Morris Animal Foundation was one of the first scientific funding organizations that recognized the power of immunotherapy, and this is reflected in our funding of innovative projects using exciting new technologies to treat a wide variety of cancers.

Projects currently in progress include:

Looking at stimulators of toll-like receptors, molecules found on cells that, when stimulated, are involved in non-specific anti-cancer immunity. The research team is beginning to test the most promising stimulator in dogs with cancer.

Identifying mutations in canine mast cell tumors that can be used as targets for immunotherapy.

Learning more about checkpoint molecules that suppress anti-cancer immune responses.

Immunotherapies are the next generation of cancer treatments. Biomedical researchers have made great strides in human immunotherapies and Morris Animal Foundation is ensuring that great strides also will be made in immunotherapy treatments for our dogs, cats, horses and even wildlife.